1. Field of the Invention
The present invention relates to a telephone apparatus, and more particularly to a telephone apparatus which includes at least two processors and provides supplementary services as well as a voice communication service through a public telephone network or the Internet, and a method for controlling the same.
2. Description of the Related Art
Generally, a telephone apparatus has been used as basic equipment for conducting a telephone conversation by transmitting and receiving voice signals to/from another party through a public telephone network or the Internet. A noticeable progress of technologies associated with the Internet has allowed the telephone apparatus to send and receive E-mails and short message service (SMS) messages. In order to send and receive the E-mails and SMS messages in a wired telephone terminal, the telephone apparatus needs to use at least two processors. This is because it is necessary to efficiently control the generation of uniform resource locators (URLs), mail accounts and SMS messages, the operation of a modem, etc., in a distributed manner, as well as a voice communication function.
A representative example of such a composite telephone apparatus is shown in Korean Patent Application No. 2001-61064 filed on Sep. 29, 2001 by this applicant and entitled SYSTEM AND METHOD FOR PROVIDING TELEPHONE NUMBER-BASED E-MAIL SERVICE AND TELEPHONE USING THE SAME. In this application, there is provided a system comprising a sub-controller (described as an “SMS processor” in this application) for performing various control operations required for voice communication, and a main controller for mainly controlling the entire operation of a multifunctional telephone, including an operation of controlling the sending of E-mails and SMS messages. The sub-controller controls a basic operation of the telephone to generate a dual tone multi-frequency (DTMF) signal, and a specific operation to generate SMS messages. The main controller controls the generation of the E-mails and SMS messages, and the operation of a modem.
Such a multifunctional telephone apparatus having two processors as mentioned above, that is, a main controller and sub-controller, is constructed to operate various circuits by an external supply voltage. For example, the telephone apparatus is constructed to operate the respective circuits with a DC voltage of a predetermined level outputted from a DC adapter. This composite telephone apparatus, which operates its internal respective circuits with the external supply voltage, is adapted to maintain a basic telephone function of a handset as it is by a −48V speech loop voltage supplied over a telephone line when the external supply voltage is not inputted due to a power failure, etc. This is typically called a no power operation (NPO) function.
The operation of the telephone apparatus can be performed in such an NPO mode by full-wave rectifying the loop voltage and supplying the resulting voltage to the sub-controller (typically, a 4-bit microcomputer) which controls the basic telephone function.
In the telephone apparatus, however, when the external supply voltage is again supplied owing to the power failure recovery during a call connection in the NPO mode, the main controller, which includes a higher-level processor than that of the sub-controller, boots a program masked in a read only memory (ROM) area in response to a power-on reset signal to initialize the sub-controller and peripheral circuits controlled thereby. As a result, the telephone apparatus has a disadvantage in that the call connection in the NPO mode is not maintained and the apparatus is not operated until the booting by the main controller is completed. Namely, if the external supply voltage is again supplied owing to the power failure recovery in the NPO mode, the call connection state is not maintained, thereby causing great inconvenience to a user.